1. Field of the Invention
The invention relates to a gear machining apparatus.
2. Description of the Related Art
A machining method described in Japanese Patent Application Publication No. 2012-45687 (JP 2012-45687 A), for example, is an effective technique for creating internal teeth or external teeth on a work piece by cutting using a machine tool such as a machining center. The machining method involves synchronously rotating a machining tool that is rotatable around a central axis (tool axis) and a work piece that is rotatable around a central axis (work piece axis) inclined at a predetermined angle to the tool axis of the machining tool, and feeding the machining tool in the direction of the work piece axis of the work piece a plurality of times to cut the work piece so as to create teeth on the work piece.
The machining tool used in this machining method is provided with a plurality of protruding tool edges by which the work piece can be cut by a predetermined amount during one feeding operation in the direction of the work piece axis. The protruding tool edges are all formed to have a flat (stepless) radial outer face (edge face) and the same edge width. Since the same parts of the protruding tool edges come into contact with the work piece from roughing to finishing, the parts are significantly worn off and the tool is short-lived. The worn-off protruding tool edges may be re-polished. However, an envelope of the edge faces of the protruding tool edges is shaped like a conical surface, and thus, the re-polishing tends to reduce the accuracy of the protruding tool edges.
Japanese Patent Application Publication No. 2005-66815 (JP 2005-66815 A) describes a machining tool for a gear that is formed to have such an edge profile contour in a section perpendicular to the axis of tool edges that is determined using a predetermined method and that allows maintaining the accuracy of the tool edges even after the worn-off tool edges are re-polished.
For the machining tools in JP 2012-45687 A and JP 2005-66815, operations from roughing through finishing are sequentially performed. Consequently, a reduction in machining time is limited. The machining tool described in JP 2005-66815 A is a shaper machining tool and is not applicable to the method in which the machining tool and the work piece are synchronously rotated to create teeth by cutting as described in JP 2012-45687 A.